PHY 206 Spring 2003 – HW #1, Chapter 1
(Problems with ** are graded.)
2.
6.
**In a calculation you end up with m/s in the numerator and m/s2 in the denominator.
The final units are (d) s., since (m/s)/(m/s2) = s
Find the correct SI units for the following constants:
a) x = C1 + C2t LHS is in meters, so C1 is in meters and C2t is in meters, meaning that C2 is in
meters/second.
b) x = ½ C1t2 LHS is in meters, so C1 is in m/s2 .
c) v2 = 2C1x LHS is in m2/s2 and x is in meters, so C1 is in m/s2
d) x = C1 cos C2 t LHS is in meters, so C1 must also be in meters, as the cosine is dimensionless. The
argument of the cosine is dimensionless, so C2 has units of sec.-1 .
11.
Complete the following:
a) 100 km/h = 100 km/h  (1mi/1.61km) = 62.1 mi/h
b) 60 cm = 60 cm  (1 in./2.54 cm) = 23.6 in.
c) 100 yd. = 100 yd.  (0.9144 m/ 1 yd.) = 91.44 m.
14.
Complete the following:
a) 1.296  105 km/h2 = 1.296  105 km/h2  (1 h. / 3600 s.) = 36 km/hs
b) 1.296  105 km/h2 = 1.296  105 km/h2  (1 h. / 3600 s.)2  (1000 m/1 km) = 10m/s2
c) 60 mi/h = 60 mi/h  (1 h. / 3600 s.)  (5280 ft./mi. ) = 88 ft./s.
d) 60 mi/h = 88 ft./s.  (0.3048 m./ft.) = 26.8 m/s
29.
The prefix mega means (d) 106.
33.
**Express the following as decimal numbers without using scientific notation:
a) 3104 = 30,000
b) 6.210-3 = 0.0062
c) 410-6 = 0.000004
d) 2.17105 = 217,000
39.
Perform the following calculations and round off the numbers:
(See answers in back of text; note that for part b) the number 2 is exact when written without a decimal
point at all. That is, it could be taken to have an infinite number of decimal points, and the significant
figures are dictated by the 0.76 term.)
44.
**Convert the following:
100 km/h = 100 km/h  (1mi/1.61km) = 62.1 mi/h
50.
**Six million barrels of imported oil per day, each 1 m. high. b) Tankers can hold 250,000 barrels. How
many tankers do we need per year for our imported oil? c) At $20 per barrel, how much do we spend per
year for imported oil?
a) (6  106 barrels)  (1 m/barrel)  ( 1 km/1000m) = 6000 km.
b) (6  106 barrels/day)  (365 days/yr)  (250,000 barrels/tanker) = 8760 tanker loads
c) (6  106 barrels/day)  (365 days/yr)  (20 dollars/barrel) = $4.38  1010 (43.8 billion dollars)
51.
**We generate 10 billion tons of solid waste, at about 1 cubic meter per ton of landfill space. How many
square miles is that if the waste is stored at an average height of 10 meters?
Area = Volume/Height = 10  109m3/10 m = 1  109 m2
1  109 m2 = (1  109 m2)  (1 mi./1610 m.)2 = 386 sq. mi.
57.
If we estimate that each person uses 10 cans each week, then in one year (with the population of
280,000,000) we find:
a) # of cans/yr. = 10 cans/wk.  52 weeks/yr  2.8 108 people = 1.46 1011 cans
b) Each can has a mass of 0.018 kg, so the total is 1.46 1011 cans  0.018 kg/can =
2.62  109 kg
c) At $1/kg, this is worth $2.62 billion.